7024 - Laserfiche WebLink

Home Browse Search

for endangered fishes can proceed using combinations of empirical studies, analyt- ical models, computer simulations, and subjective assessments to assist the deci- sion-making process (Maguire 1986; Soule 1987). CONCLUSIONS Instream flow requirements for endan- gered fishes should be determined with respect to their recovery, not survival. This is particularly true in the Colorado River where habitat change has been severe and widespread, and is continuing. Survival is too often synonymous with "status quo," and this may ultimately lead to extinction in declining populations. In the past, stream flows for fisheries resources have been provided on a minimum flow basis, and the utility of this approach is ques- tionable (Stalnaker 1990). Although much progress has been made in developing analytical methods for as- sessing streamflows, the relationship be- tween physical parameters and fish produc- tion is complex and not well understood. New approaches for assessing streamflow requirements of fishes are needed if en- dangered fish recovery is to become a re- ality. Rather than providing endangered fish with the same habitats in which they are declining, alternatives might include studies that would test fish community re- sponse to various flow scenarios. These could include appropriately designed lab- oratory studies, reclamation of stream sec- tions, or construction of new stream sec- tions in which such things as flows and species compositions could be manipulat- ed to test specific hypotheses concerning fish response to flows. The goal of these studies should be to determine if flows are limiting the recovery of different life stages of the endangered fishes and to evaluate the role of "non flow" impacts. Because ex- perimental approaches are complex and costly, they will not become a reality un- less managers are better informed about shortcomings and potential dangers of us- ing some instream flow methods. Although most of the interest in deter- mining and protecting Colorado River fishes has been associated with the need to protect federally listed endangered spe- cies, the "fundamentally insular" (Molles 1980) nature of the fauna suggests that oth- er species may also become endangered or extinct in the near future. As each species disappears, it is anticipated that recovery of the remaining forms will become in- creasingly more difficult as perturbations in the native ecosystem increase. Successful recovery of the Colorado Riv- er fishes to a self-sustaining status will re- quire the efforts of many individuals with varied interests concerning multiple uses of water. Because some of these interests will differ, progress will be made only by concentrating on the consequences of wa- ter management decisions. Such decisions must be based on a recovery flow philos- ophy grounded in sound ecological prin- ciples and solid biological information. Acknowledgments I thank the Bureau of Reclamation, Fish and Wildlife Service, National Park Service, and other agencies and universities that have supported re- search and management activities on endangered Colorado River fishes. Additionally, I thank C. A. Karp, J. Hamill, and three anonymous reviewers for their comments on earlier drafts of the manu- scri pt. REFERENCES Baltz, D. M., B. Vondracek, 1. R. Brown, and P. B. Moyle. 1987. Influence of temperature on microhabitat choice by fishes in a California stream. Transactions of the American Fisheries Society 116(1):12-20. Baxter, G. T., and J. R. Simon. 1970. Wyoming fishes. Cheyenne: Wyoming Game and Fish Department (Bulletin 4). Beecher, H. A. 1990. Standards for instream flows. Rivers 1(2):97-109. I H. M. Tyus 33 I rt